/*
 * @(#)PolicyFinderModule.java
 *
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 * This software is provided "AS IS," without a warranty of any kind. ALL
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package org.wso2.balana.finder;

import org.wso2.balana.ctx.EvaluationCtx;
import org.wso2.balana.PolicyMetaData;
import org.wso2.balana.VersionConstraints;

import java.net.URI;

/**
 * This is the abstract class that all <code>PolicyFinder</code> modules extend.
 * All methods have default values to represent that the given feature isn't
 * supported by this module, so module writers needs only implement the methods
 * for the features they're supporting.
 * 
 * @since 1.0
 * @author Seth Proctor
 */
public abstract class PolicyFinderModule {

	/**
	 * Returns this module's identifier. A module does not need to provide a
	 * unique identifier, but it is a good idea, especially in support of
	 * management software. Common identifiers would be the full package and
	 * class name (the default if this method isn't overridden), just the class
	 * name, or some other well-known string that identifies this class.
	 * 
	 * @return this module's identifier
	 */
	public String getIdentifier() {
		return getClass().getName();
	}

	/**
	 * Returns true if the module supports finding policies based on a request
	 * (ie, target matching). By default this method returns false.
	 * 
	 * @return true if request retrieval is supported
	 */
	public boolean isRequestSupported() {
		return false;
	}

	/**
	 * Returns true if the module supports finding policies based on an id
	 * reference (in a PolicySet). By default this method returns false.
	 * 
	 * @return true if idReference retrieval is supported
	 */
	public boolean isIdReferenceSupported() {
		return false;
	}

	/**
	 * Initializes this module for use by the given finder. Typically this is
	 * called when a <code>PDP</code> is initialized with a
	 * <code>PDPConfig</code> containing the given <code>PolicyFinder</code>.
	 * Because <code>PolicyFinderModule</code>s usually need to parse policies,
	 * and this requires knowing their <code>PolicyFinder<code>,
	 * parsing is usually done at or after this point in the lifetime
	 * of this module. This might also be a good time to reset any internal
	 * caches or temporary data. Note that this method may be called more
	 * than once in the lifetime of a module.
	 * 
	 * @param finder
	 *            the <code>PolicyFinder</code> using this module
	 */
	public abstract void init(PolicyFinder finder);

	/**
	 * This is an experimental method that asks the module to invalidate any
	 * cache values it may contain. This is not used by any of the core
	 * processing code, but it may be used by management software that wants to
	 * have some control over these modules. Since a module is free to decide
	 * how or if it caches values, and whether it is capable of updating values
	 * once in a cache, a module is free to intrepret this message in any way it
	 * sees fit (including igoring the message). It is preferable, however, for
	 * a module to make every effort to clear any dynamically cached values it
	 * contains.
	 * <p>
	 * This method has been introduced to see what people think of this
	 * functionality, and how they would like to use it. It may be removed in
	 * future versions, or it may be changed to a more general message-passing
	 * system (if other useful messages are identified).
	 * 
	 * @since 1.2
	 */
	public void invalidateCache() {

	}

	/**
	 * Tries to find one and only one matching policy given the request
	 * represented by the context data. If more than one policy is found, this
	 * is an error and must be reported as such. If no policies are found, then
	 * an empty result must be returned. By default this method returns an empty
	 * result. This method should never return null.
	 * 
	 * @param context
	 *            the representation of the request
	 * 
	 * @return the result of looking for a matching policy
	 */
	public PolicyFinderResult findPolicy(EvaluationCtx context) {
		return new PolicyFinderResult();
	}

	/**
	 * Tries to find one and only one matching policy given the idReference If
	 * more than one policy is found, this is an error and must be reported as
	 * such. If no policies are found, then an empty result must be returned. By
	 * default this method returns an empty result. This method should never
	 * return null.
	 * 
	 * @param idReference
	 *            an identifier specifying some policy
	 * @param type
	 *            type of reference (policy or policySet) as identified by the
	 *            fields in <code>PolicyReference</code>
	 * @param constraints
	 *            any optional constraints on the version of the referenced
	 *            policy (this will never be null, but it may impose no
	 *            constraints, and in fact will never impose constraints when
	 *            used from a pre-2.0 XACML policy)
	 * @param parentMetaData
	 *            the meta-data from the parent policy, which provides XACML
	 *            version, factories, etc.
	 * 
	 * @return the result of looking for a matching policy
	 */
	public PolicyFinderResult findPolicy(URI idReference, int type,
			VersionConstraints constraints, PolicyMetaData parentMetaData) {
		return new PolicyFinderResult();
	}

}
